Optoelectronic mounting structure

ABSTRACT

An optoelectronic mounting structure is provided that may be used in conjunction with an optical transmitter, receiver or transceiver module. The apparatus comprises: (1) a mounting structure; (2) an array of optoelectronic devices adapted to the mounting structure, the optoelectronic devices having at least a first end; (3) an array of optical elements, the array of optical elements having at least a first end; (4) the first end of the array of optical elements proximate to the first end of the array of optoelectronic devices in such a manner that one or more optical elements is optically aligned to one or more optoelectronic devices; and (5) a heat spreader passing along a surface of a head region of the mounting structure. The mounting structure may be a flexible printed circuit board. Thermal vias or heat pipes in the head region may transmit heat from the mounting structure to the heat spreader. The heat spreader may provide mechanical rigidity or stiffness to the heat region. In another embodiment, an electrical contact and ground plane may pass along a surface of the head region so as to provide an electrical contact path to the optoelectronic devices and limit electromagnetic interference. In yet another embodiment, a window may be formed in the head region of the mounting structure so as to provide access to the heat spreader. Optoelectronic devices may be adapted to the heat spreader in such a manner that the devices are accessible through the window in the mounting structure.

FIELD OF THE INVENTION

[0001] This invention relates to an optoelectronic mounting structurethat may be used in conjunction with an optical transmitter, receiver ortransceiver module.

BACKGROUND OF THE INVENTION

[0002] Fiber optics are one of the most important new media fortransmitting information. Fiber optics are capable of carrying enormousquantities of voice, data and video traffic on light impulses overhair-thin glass fibers. Fiber optics transmit more information and dataover a shorter period of time than circuit-transmission media. Forexample, optical signals may be transmitted over fiber optics withlosses of less than 0.1 dB/km. In sharp contrast, data generally istransmitted over a pair of twisted copper wires with losses of up to 50dB/km. The capabilities of fiber optics have fundamentally changedcommunications.

[0003] The fiber optics industry has exploded as the Internet andtelecommunication field have created a skyrocketing demand forbroadband, high-speed pipe lines to carry data. Long-span fiber opticnetworks of 100 kilometers or more carry bandwidth ranging from 40 to 50giga bites per second. Similarly, high-speed fiber optics are capable ofconnecting wide-area networks of approximately 200 kilometers. Also,fiber optics may connect metropolitan networks of 500 meters to 2kilometers, such as connecting one building to another building. Thelargest growth area for high-speed fiber optics, however, is connectingdistances of less than 300 meters. In this sub-300 meter orshort-distance market, fiber optics are used for a wide variety ofpurposes, including connecting computers within a room and linkingrouters, switches and transport equipment.

[0004] While significant progress has been made in the area of fiberoptics, more wide-spread use is dependent upon the availability of a lowcost, easy-to-use and efficient (i.e., low loss of light) opticaltransmitter and receiver module to link fiber optics to variouselectronic devices and components such as computers and routers. Acritical aspect of such a module is the accurate alignment andattachment of the individual optical fibers to the electronic devicesthat transmit and receive light streams to and from the optical fibers.These electronic devices, known as optoelectronic devices, use opticaland electronic technology or optoelectronics to convert electricalsignals into optical radiation or light and transmit the radiation intooptical fibers. Other optoelectronic devices receive optical radiationfrom optical fibers and convert it into electrical signals forprocessing. Accurate alignment and attachment of the individual opticalfibers to the optoelectronic devices is essential to achieving a goodand efficient optical connection, one that produces a low loss of lightat the interface between the optical fibers and the optoelectronicdevices.

[0005] A known method for precisely coupling optical fibers tooptoelectronic devices is active alignment. Specifically, aphoto-detector is placed at one end of an optical fiber, and anoptoelectronic device, such as a vertical cavity surface emitting laser,is placed near the other end of the optical fiber. After turning on thelaser, the optical fiber is manipulated manually around thelight-emitting surface of the laser until the photo-detector detects themaximum amount of optical radiation as indicated by an output electricalsignal. Similarly, a photo-detector can be actively coupled to anoptical fiber by transmitting laser light into one end of an opticalfiber and manually adjusting the position of the other end of theoptical fiber relative to the photo-detector until the detector receivesthe maximum amount of optical radiation.

[0006] Actively aligning an array of optical fibers to an array ofoptoelectronic devices is not practical because the dimensions of anoptoelectronic device and the cross-section of an optical fiber aresmall and multiple dimensions of rotation and translation motion must becontrolled. The active alignment process to connect even a singleoptical fiber strand to an optoelectronic device is usuallytime-consuming and requires knowledge, skill and expertise. The activealignment process is particularly laborious and time-intensive when anumber of optical fibers must be individually aligned to an array ofoptoelectronic devices. This process requires a variety of relativelycomplex and costly components that significantly increase thefabrication costs to produce precisely aligned optical devices.Moreover, during the active alignment process, optoelectronic devicesemit a significant amount of optical power and energy. The heatgenerated by the devices can produce thermal strain that may cause theoptical fibers and the optoelectronic devices to be misaligned.

[0007] Various passive alignment techniques have been developed, such asthe use of guide pins and holes, to attempt to provide fast, easy andsimultaneous alignment and attachment of an array of optical fibers tooptoelectronic devices. Passive alignment typically indicates atechnique for aligning a laser and an optical fiber that does notrequire the laser to be turned on during the alignment process; whereasan “active” technique requires the laser to be turned on. However, thesepassive alignment techniques often do not provide a precision couplingof the optical fibers to optoelectronic devices.

[0008] Accordingly, there is a need in the art to provide a method andapparatus for precise, fast and easy alignment and attachment of opticalfibers to optoelectronic devices, which may be mounted on a circuitboard. In addition, there is a need in the art to provide an inexpensivemethod and apparatus for aligning and attaching optical fibers tooptoelectronic devices so that the method and apparatus are suitable formass production. Finally, there is a need in the art for a smallapparatus coupling optical fibers to optoelectronic devices so that theapparatus can easily be mounted on a circuit board.

SUMMARY OF THE INVENTION

[0009] In view of the above-stated disadvantages of the prior art, anobject of the present invention is to provide an optoelectronic mountingstructure that may be used in conjunction with an optical transmitter,receiver or transceiver module.

[0010] Another object of the present invention is to provide anapparatus and process for quickly, easily and precisely aligning andconnecting at least one optical fiber to at least one optoelectronicdevice by using highly precise machinery and adhesive.

[0011] Another object of the present invention is to provide anapparatus and process for aligning and connecting at least one opticalfiber to at least one optoelectronic device while maintaining a gapbetween at least one optical fiber and at least one optoelectronicdevice.

[0012] Another object of the present invention is to provide anapparatus and process for quickly, easily and precisely aligning andconnecting at least one optical fiber to a wide variety of device(s) orobject(s) by using highly precise machinery and adhesive.

[0013] Another object of the present invention is to provide aninexpensive method and apparatus for aligning and connecting at leastone optical fiber to at least one optoelectronic device so that themethod and apparatus are suitable for mass production.

[0014] Another object of the present invention is to provide aninexpensive method and apparatus for aligning and connecting at leastone optical fiber to a wide variety of device(s) or object(s) so thatthe method and apparatus are suitable for mass production.

[0015] Another object of the present invention is to provide a smallapparatus for coupling at least one optical fiber to at least oneoptoelectronic device so that the apparatus can easily be mounted on acircuit board.

[0016] In accordance with the first object of the present invention, anembodiment of an optoelectronic mounting structure comprises: (1) amounting structure; (2) an array of optoelectronic devices adapted tothe mounting structure, the optoelectronic devices having at least afirst end; (3) an array of optical elements, the array of opticalelements having at least a first end; (4) the first end of the array ofoptical elements proximate to the first end of the array ofoptoelectronic devices in such a manner that one or more opticalelements is optically aligned to one or more optoelectronic devices; and(5) a heat spreader passing along a surface of a head region of themounting structure. The mounting structure may be a flexible printedcircuit board. Thermal vias or heat pipes in the head region maytransmit heat from the mounting structure to the heat spreader. The heatspreader may provide mechanical rigidity or stiffness to the heatregion. In another embodiment, an electrical contact and ground planemay pass along a surface of the head region so as to provide anelectrical contact path to the optoelectronic devices and limitelectromagnetic interference. In yet another embodiment, a window may beformed in the head region of the mounting structure so as to provideaccess to the heat spreader. Optoelectronic devices may be adapted tothe heat spreader in such a manner that the devices are accessiblethrough the window in the mounting structure.

[0017] In accordance with other aspects of the present invention, anoptical transmitter, receiver or transceiver module is provided thatincludes a flexible printed circuit board that is bent at an angle,forming a head region, buckle region and main body region. The flexibleprinted circuit board supports the electrical components and circuitryof the present invention.

[0018] An array of optoelectronic devices, a driver or amplifier chip, aphoto-detector, conducting lines, and electronic components may bemounted on a first surface of the head region of the flexible printedcircuit board. The optoelectronic devices send and or receive light toand from optical fibers. The optoelectronic devices may be mounted ontop of a spacer that may be attached to the head region of the flexibleprinted circuit board. The spacer raises the height of theoptoelectronic devices so that they may efficiently communicate with theoptical fibers and other electrical components that are mounted on thehead region of the flexible printed circuit board. Alternatively, theoptoelectronic devices may be mounted on an optoelectronic mountingstructure that is accessible through a window in the flexible printedcircuit board. When the optoelectronic devices function as emitters foremitting optical signals into optical fibers, they may be oxide-confinedvertical cavity surface emitting lasers; if the optoelectronic devicesfunction as receivers for receiving optical signals from optical fibers,they may be photo-detectors formed on a semiconductor chip. The driveror amplifier chip modulates and drives the optoelectronic devices. Anoptical power control system may monitor, regulate and stabilize thetemperature, power and wavelength of the optoelectronic devices.Additionally, an attenuator may improve the performance of theoptoelectronic devices by attenuating the optical energy emitted fromthe devices. Similarly, a conditioner may improve the performance of theoptical fibers by conditioning the launch of the optical energy into thefibers.

[0019] The remaining electrical components and circuitry of the opticalmodule may be located on the main body region of the flexible printedcircuit board.

[0020] The buckle region of the flexible printed circuit board, theregion connecting the main body region and head region, absorbs anystress that may occur in connecting a fiber optic cable to the presentinvention and assists in providing alignment between the optical fibersand optoelectronic devices.

[0021] A first ferrule, packaging an array of optical fibers, is mountedon top of the array of optoelectronic devices on the first surface ofthe head region of the flexible printed circuit board. Highly precisemachinery optically aligns aligns the array of optical fiber in thefirst ferrule to the array of optoelectronic devices. A gap orinterstitial space is established between a second end of the firstferrule and a top surface of the optoelectronic devices. Opticaladhesive is dispensed in the space or gap between the first ferrule andthe optoelectronic devices so as to maintain the precise axial alignmentof the array of optical fibers to the array of optoelectronic devices.The optical adhesive provides a optically transparent and stable mediumbetween the optoelectronic devices and the fibers.

[0022] After the optical adhesive is cured, a dam may be formed on thefirst surface of the head region of the flexible printed circuit board.A second adhesive is dispensed inside the dam, and the second adhesivefurther mechanically stabilizes the first ferrule to the flexibleprinted circuit board. The second adhesive also protects the circuitryin the immediate vicinity of the optical fibers and optoelectronicdevices. For airtight sealing of the optical module, the surface area ofthe second adhesive may be covered with a third layer, such as a gelsilicon resin.

[0023] After the first ferrule is firmly attached to the head region ofthe flexible printed circuit board, the circuit board is wrapped aroundand attached to a circuit board mounting structure with an adhesive.

[0024] A housing snaps or otherwise mounts with screws, adhesives orother means onto a first end of the circuit board mounting structure,enclosing the head region of the flexible printed circuit board alongwith the first ferrule that is mounted on the head region. The firstferrule fits inside a longitudinal cavity extending from a first end ofthe housing to a second end of the housing. Ridges inside thelongitudinal cavity grab and hold the first ferrule in place.

[0025] In operation, a fiber optic cable from an external system isbrought in proximity to the housing to create an optical connection. Asecond ferrule is located at one end of the fiber optic cable, and thesecond ferrule is designed to mate with the second end of the housing.The second ferrule is inserted into the second end of the housing andridges in the housing's longitudinal cavity engage and hold the secondferrule in place. Once inside the longitudinal cavity, the secondferrule mates with the first ferrule by engaging guide pins located on afront end of the first ferrule with guide holes located on a front endof the second ferrule. As a result, the array of optical fibers packagedin the two ferrules are axially aligned. Upon mating the ferrulestogether, light may be transmitted from the fiber optic cable throughthe two ferrules and to the optoelectronic devices that are adapted tothe flexible printed circuit board. The optoelectronic devices convertthe light into electrical signals for processing and vice versa.

[0026] A further significant aspect of the present invention involves aprocess by which the first ferrule is aligned and connected to the arrayof optoelectronic devices, according to a preferred embodiment of theinvention. A process of aligning and connecting the first ferrule to thearray of optoelectronic device comprises the following steps:

[0027] 1. Aligning the optical fiber(s) packaged in the first ferrulewith the optoelectronic device(s) so that each optical fiber isoptically aligned to a corresponding optoelectronic device(s);

[0028] 2. Depositing optical adhesive on a top surface of theoptoelectronic device(s);

[0029] 3. Placing the first ferrule on top of the optical adhesive whilemaintaining the alignment of step 1;

[0030] 4. Tacking and curing the optical adhesive; and

[0031] 5. Forming a dam around the first ferrule that is mounted on thehead region of the flexible printed circuit board, dispensing adhesiveand curing the adhesive.

[0032] Although the above-stated process has been discussed in terms ofaccurately aligning and attaching the first ferrule to the array ofoptoelectronic devices, the same process may be used to accurately alignand attach a single optical fiber or an array of optical fibers to asingle optoelectronic devices or an array of optoelectronic devices.Similarly, the process may be used to accurately align and connect atleast one optical element to a wide variety of devices and objects otherthan optoelectronic devices. The optical element may comprise a lensletarray, diffractive optic array or an optical fiber. For example, theprocess may be used to connect an optical element to amicro-electromechanical system (“MEMS”) or a biological or chemicalsample held on a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention, and together with the general description given above and thedetailed description of the embodiments given below, serve to explainthe principles of the invention.

[0034]FIG. 1 is perspective view of an embodiment of the invention.

[0035]FIG. 2 shows a perspective view of an embodiment of the inventionmounted on the edge of a circuit board.

[0036]FIGS. 3a-3 b are diagrams of cut-away-side views of the flexibleprinted circuit board, according to an embodiment of the invention.

[0037]FIG. 4 is a diagram of an embodiment of the optical power controlsystem, according to an embodiment of the invention.

[0038]FIGS. 5a-5 d are diagrams of different optical beam patterns on anaperture of a photo-detector, according to an embodiment of theinvention.

[0039]FIGS. 6a-6 b are diagrams of alternative embodiments of theoptical power control system, according to an embodiment of theinvention.

[0040]FIGS. 7a-7 b are cut-away-side views showing embodiments of a headregion of the flexible printed circuit board, according to embodimentsof the invention.

[0041]FIG. 8 is side-view showing an alternative embodiment of a firstferrule and the head region of the flexible printed circuit board,according to an embodiment of the invention.

[0042]FIG. 9 is an exploded view of an embodiment of the housing, anembodiment of the first ferrule, an embodiment of a circuit boardmounting structure and an embodiment of the flexible printed circuitboard, according to an embodiment of the invention.

[0043]FIG. 10 is a three-dimensional view of an embodiment of thehousing, according to an embodiment of the invention.

[0044]FIGS. 11a-11 b are diagrams of an embodiment of an apparatus forholding an optical element, according to an embodiment of the invention.

[0045]FIGS. 12a-12 d show views of images of optoelectronic devices andimages of optical fibers under the high magnification of a split-fieldmicroscope. FIG. 13 shows the display on a monitor of a video imagemeasuring system.

DETAILED DESCRIPTION

[0046] I. Introduction

[0047] The following embodiments will be described in the context of anoptical transceiver, receiver or transceiver module and a method ofmaking the same. Those skilled in the art, however, will recognize thatthe disclosed methods and structures are adaptable for broaderapplications. If the same reference numeral is repeated with respect todifferent figures, it refers to the corresponding structure in eachfigure.

[0048] With reference to FIG. 1, an optical transmitter, receiver ortransceiver module 100 is depicted, according to an embodiment of theinvention. The optical module 100 comprises a flexible printed circuitboard 102 that wraps around and attaches to a circuit board mountingstructure 104. The flexible printed circuit board 102 functions tosupport the electrical components of the optical module 100, such as anarray of optoelectronic devices 106, a driver or amplifier chip 108, anda photo-detector 110. A first ferrule 112, packaging an array of opticalfibers 114, is mounted on top of the array of optoelectronic devices 106in such a manner that one or more of the optical fibers in the array isoptically aligned to one or more of the optoelectronic devices.

[0049] Prior to mounting the first ferrule 112 on the array ofoptoelectronic devices 106, a first adhesive 116 is dispensed on a topsurface of the array of optoelectronic devices 106. The first adhesive116 functions to maintain the precise axial alignment between the arrayof optical fibers 114 and array of optoelectronic devices 106. The firstadhesive 116 also functions to produce a high, optical couplingefficiency between the optical fibers 114 and optoelectronic devices106. Additionally, the first adhesive 116 functions to mechanicallystabilize the first ferrule 112 to the optoelectronic devices 106.

[0050] To further mechanically stabilize the first ferrule 112 to theflexible printed circuit board 102, a dam 120 may be formed on theflexible printed circuit board 102 and filled with a second adhesive122. An housing 124 is attached to the circuit board mounting structure104, surrounding and enclosing the first ferrule 112 that is connectedto the flexible printed circuit board 102.

[0051] In an illustrative embodiment, an optical transmitter or receivermodule 100 is mounted on a second circuit board 202, as depicted in FIG.2. The optical module, however, does not have to be mounted at theboard's edge. The optical module may be mounted anywhere on the circuitboard so long as there is room for connecting the optical module to theexternal environment. In operation, the optical module 100 is connectedto the external environment by connecting a fiber optic cable 204 to theoptical module 100. This is accomplished by plugging a second ferrule206 that is attached to one end of a fiber optic cable 204 into theoptical module 100. Once the second ferrule 206 is plugged into theoptical module 100, the module 100 is optically connected to the fiberoptic cable 204. Accordingly, if the optical module 100 functions as atransmitter, the optical module 100 receives electrical signals from thesecond circuit board 202, converts the electrical signals into opticalsignals, and transmits the optical signals into the fiber optic cable204. On the other hand, if the optical module 100 functions as areceiver, the optical module 100 receives optical signals from the fiberoptic cable 204, converts the optical signals into electrical signalsand transmits the electrical signals to the second circuit board 202.

[0052] II. Flexible Printed Circuit Board

[0053] The flexible printed circuit board 102 is now described infurther detail. Specifically, FIG. 3a is a cut-away-side view of anembodiment of the flexible printed circuit board 102. The flexibleprinted circuit board may be bent or folded in any direction, andanother embodiment of the flexible printed circuit board is shown inFIG. 3b. The flexible printed circuit board 102 is thin, rectangular andflexible with various edge contours, and it is composed of flexiblemetal layers that are sandwiched between insulating layers. The entireflexible printed circuit board may be composed of this multi-layeredstructure. In addition to supporting the electrical components andcircuitry of the optical module 100, the flexible printed circuit board102 also provides stress relief when connecting the optical module 100to an external source and aids in maintaining the precise alignment ofthe optoelectronic devices 106 with an the optical fibers 114.

[0054] The flexible printed circuit board 102 is bent in the “Y”direction to form a head region 302, a buckle region 304 and a main bodyregion 306. The head region 302 may function to support the keyelectrical components and other elements of the optical module 100, suchas the optoelectronic devices 106 and driver or amplifier chip 108. Themain body region houses a plurality of electronic components 308 and aplurality of electronic circuitry of the optical module 100. The buckleregion 304 is that area of the flexible printed circuit board 102 thatconnects the head region 302 to the main body region 306.

[0055] Each region of the flexible printed circuit board is described indetail below.

[0056] A. Head Region

[0057] The head region 302 of the flexible printed circuit board 102 isnow described in detail, and it is shown in FIG. 3a or FIG. 3b. The headregion 302 is composed of the same multi-layered structure as the otherregions of the flexible printed circuit board 102. The head region 302is orientated in the “Y” direction, and the head region 302 may be on aplane that is substantially perpendicular to the main body region 306 ofthe flexible printed circuit board 102, as shown in FIG. 3a or FIG. 3b.

[0058] The head region 302 is orientated in the “Y” direction so thatthe optical fibers 114 packaged in the first ferrule 112 are opticallyaligned with the optical fibers 114 packaged in the second ferrule 206.As shown in FIG. 3a or FIG. 3b, the head region 302 of the flexibleprinted circuit board 102 may function to support the key electricalcomponents of the optical module 100 such as the driver or amplifierchip 108.

[0059] The flexible printed circuit board performs the function ofchanging the plane on which the signals are received. Specifically, thesignals are received by the flexible printed circuit board in the “X”direction from the first ferrule 112 that is optically connected to theoptoelectronic devices 106, which are adapted to the head region 302 ofthe flexible printed circuit board 102. The signals then flow insubstantially the “Y” direction in the head region 302 of the flexibleprinted circuit board 102. The signals then change planes, as they passfrom the head region 302 through the buckle region 304 and to the mainbody region 306 of the flexible printed circuit board 102, as shown inFIG. 3a or FIG. 3b. The signals flow in the “X” direction in the mainbody region. Advantageously, by changing the plane on which the signalstravel, the flexible printed circuit board functions to efficientlycommunicate with both the fiber optical cable attached to the opticalmodule and an external circuit board upon which the optical module ismounted.

[0060] 1. Optoelectronic Devices

[0061] One board-level component of the head region 302 may be the arrayof optoelectronic devices 106. The array of optoelectronic devices 106may be adapted approximately in the center of a first surface 310 and/orthe second surface 704 of the head region 302, as shown in FIG. 3a orFIG. 3b. The array of optoelectronic devices 106 may be aone-dimensional, two-dimensional or a multi-dimensional array ofoptoelectronic devices 106.

[0062] The array of optoelectronic devices 106 may be various types ofdevices such as edge-emitting lasers, light-emitting diodes (“LEDs”),vertical cavity surface emitting lasers (VCSELs), other surface emittingdevices or photo-detectors. The optoelectronic devices 106 may also beintegrated devices combining one or more devices such as the combinationof VCSELs and transistors or photo-detectors and transistors (or VCSELs,photo-detectors and transistors). The optoelectronic devices 106 mayalso be a heterogeneous array where some of the array elements areemitters and some are detectors.

[0063] If the optoelectronic devices 106 are VCSELs, the optical module100 functions as a transmitter, sending optical signals into the arrayof optical fibers 114 that are packaged in the ferrule.

[0064] If the optoelectronic devices 106 are photo-detectors formed on asemiconductor chip, the optical module 100 functions as a receiver forreceiving optical signals from the array of optical fibers 114 packagedin the first ferrule 112.

[0065] In an embodiment, the optoelectronic devices 106 areoxide-confined VCSELs. Advantageously, oxide-confined VCSELs operate athigher speeds and have lower threshold currents than non-oxide VCSELs,such as ion-implant VCSELs. Additionally, oxide-confined VCSELs arestable VCSELs, exhibiting uniform power and wavelength performance overvarying temperature ranges. This advantageously would allow the moduleto perform for longer a duration and high degree of accuracy. Moreover,it is contemplated that use of oxide VCSELs would obviate the need for afeedback loop, as hereafter described. Moreover, oxide-confined VCSELsallow the fabrication of highly uniform arrays, enabling multi-channel,parallel optic applications.

[0066] Lastly in another embodiment, a micro-electromechanical system(“MEMS”) array, a micro-pipette array or a biological or chemical sampleheld on a substrate may be used in place of the array of optoelectronicdevices 106.

[0067] 2. Driver or Amplifier Chip

[0068] Another board-level component of the head region 302 of theflexible printed circuit board 102 may be the driver or amplifier chip108, as shown in FIG. 3a or FIG. 3b. Specifically, a driver or amplifierchip 108 may be adapted next to the array of optoelectronic devices 106on the first surface 310 and or the second surface 704 of the headregion 302 of the flexible printed circuit board 102, as shown in FIG.3a or FIG. 3b. In another embodiment, the driver or amplifier chip 108may be adapted to the main body region of the flexible printed circuitboard.

[0069] Where the optoelectronic devices 106 are VCSELs, a driver chip isused, and it functions to drive and modulate the VCSELs. Where theoptoelectronic devices 106 are photo-detectors, then an amplifier chipis used, and it amplifies the electronic signals received fromphoto-detectors. Wire bonds 312 or any other suitable means such asplating, welding, tape-automated bonding or the use of flip-chiptechnology may be used to connect the driver or amplifier chip 108 tothe optoelectronic devices 106, as shown in FIG. 3a or FIG. 3b. Thedriver or amplifier chip 108 may be monolithically formed on asemiconductor chip or integrated with the array of optoelectronicdevices 106 as a hybrid circuit.

[0070] 3. Optical Power Control System

[0071] Still another board-level component of the head region 302 of theflexible printed circuit board 102 may be an optical power controlsystem. During operation, temperature changes across an array of VCSELsand other factors can cause the power and wavelength of the VCSEL arrayto change. The optical power control system functions to stabilize theperformance of the array of VCSELs over changing conditions.Specifically, if the array of optoelectronic devices 106 aretransmitters such as VCSELs, an optical power control system is adaptedproximate to the array of optoelectronic devices 106 on the firstsurface 310 of the head region 302 of the flexible printed circuit board102.

[0072]FIG. 4 is an embodiment of the optical power control system. Theoptical power control system utilizes the photo-detector 110 (oralternatively a light-pipe) to measure the optical output power of aVCSEL in an array of VCSELs. In an embodiment of the invention, if theoptoelectronic devices 106 are VCSELs, the optical power control systemmeasures the power of a thirteenth VCSEL 404 in the array of VCSELs.However, the optical power may be measured by any other suitable VCSELin the array of VCSELs. The photo-detector's measurement is used toadjust the electrical power input to each individual VCSEL. This isaccomplished by a feedback loop between the photo-detector 110 and thedriver chip 108. The driver chip 108 adjusts the laser injection currentin response to the feedback, and this results in a stable array ofoptoelectronic devices.

[0073]FIGS. 5a-5 d are diagrams of different optical beam patterns onapertures of photo-detectors. A critical aspect of a robust opticalpower control system is the tracking ratio. The tracking ratio is theability of the photo-detector 110 to track and capture the optical beam408 so that the photo-detector 110 accurately measures the amount ofpower emitted by the VCSEL array. In the ideal situation, the opticalbeam 408 is fully captured by the photodetector's aperture 502 as shownin FIG. 5a. This allows the photo-detector 110 to precisely measure thepower of the beam. However, temperature changes, aging, and otherfactors during operation can cause the optical beam 408 to becomemisaligned, as shown in FIG. 5b. Since the photo-detector's aperture 502captures less of the optical beam 408, the photo-detector is unable toaccurately measure the beam's power. This causes the optical powercontrol system to improperly adjust the power of the VCSEL array.Similarly as shown in FIG. 5c, changes in laser injection current andother factors can create a diverged or enlarged optical beam 504. Again,the photo-detector's aperture 502 detects less power, causing inaccurateadjustments to the power output of the VCSEL array.

[0074] Advantageously, the present invention improves the tracking ratiounder changing conditions. The present invention accomplishes this taskby adapting a reflector/scatterer 410 to a second end of the firstferrule 320, as shown in FIG. 4. An optical path may be created from thethirteenth VCSEL 404 to the reflector/scatterer 410 and onto thephoto-detector 110. The geometry and surface roughness of thereflector/scatterer 410 produces a beam pattern 506 that is highlyuniform, scattered and larger than the photo-detector's aperture, asshown in FIG. 5d. This uniform and scattered beam pattern 506 has a hightolerance for alignment and divergence changes. Accordingly, it is lesssensitive to temperature changes, aging and other issues.Advantageously, this allows the photo-detector 110 to accurately measurethe power of the optical beam 408 under varying conditions andenvironmental circumstances. For example, temperature changes across theVCSEL array may change the optical beam's pattern, alignment anddivergence, and this impacts the photo-detector's 110 ability toaccurately measure power. However, the highly scattered and uniform beampattern produced by the reflector/scatterer 410 is significantly lesssensitive to temperature changes. This allows the photo-detector 110 tocapture the optical beam 504 and accurately measure power. The novelbeam pattern produced by the unique reflector/scatterer 410 allows theoptical power control system to maintain constant power across the VCSELarray under changing conditions. Consequently, the optical power controlsystem produces a stable and uniform VCSEL array.

[0075] In an embodiment, the reflector/scatterer 410 is a conical holethat is coated with a reflecting/scattering coating. Thereflective/scattering coating may be gold, titanium, aluminum or othertypes materials that have the effect of both reflecting and scatteringlight. The reflector/scatterer 410 may also be an arbitrarily shapedrough surface, sphere, notch, prism or optical element.

[0076] An alternative embodiment of the optical power control system isshow in FIG. 6a. A glob top of optical resin 602 is coated with areflective scatterer and is dispensed on the top surface of the array ofoptoelectronic devices 106 and a top surface of the photo detector 606.The glob top 602 scatters light in multiple directions, and a portion ofthe light is detected by the photo-detector 110. The shape and coatingof the glob top 602 may be engineered to provide varying amounts ofscattering for more uniformity and reflection and thus higher energytransfer. As shown by dashed lines in FIG. 6a, a notch may be cut in thefirst ferrule 112 to allow room for the glob top of optical resign.

[0077] Another embodiment of the optical power control system is show inFIG. 6b. Here, a reflector 608 is formed separately and then adapted tothe top surface of the array of optoelectronic devices 106 and to thetop surface of the photo detector 606. Similar to the glob top 602, thereflector 608 scatters light in multiple directions, and a portion ofthe light is detected by the photo-detector 110. The shape and coatingof the reflector 608 may be engineered to provide varying amounts ofscattering for more uniformity and reflecting and thus higher energytransfer. The reflector may be in the shape of an ellipsoid,three-dimensional conical hole or other shape. It also may be ageometrically-shaped object. In another embodiment, the reflector isadapted to the second end 320 of the first ferrule 112 rather thanadapted to the top surface of array of optoelectronic devices 106 andphoto detector 606. As shown by dashed lines in FIG. 6a, a notch may becut in the ferrule to allow room for the glob top of optical resign.

[0078] 4. Spacer

[0079] An additional board-level component of the head region 302 of theflexible printed circuit board 102 may be a spacer 314, as shown in FIG.3a or FIG. 3b. The spacer 314 may be shaped like a square and may becomposed of silicon material. A bottom surface of the spacer 314 may beadapted approximately in the center of the head region 302, as shown inFIG. 3a or FIG. 3b. A top surface of the spacer 314 may serve as amounting surface for the array of optoelectronic devices 106 when theyfunction as receivers (e.g., photo-detectors). The spacer 314 isoptional if the optoelectronic devices 106 function as emitters (e.g.,VCSELs). The spacer also may function as a mounting surface for othercomponents such as the first ferrule 112.

[0080] The spacer 314 may function to raise the height of the array ofoptoelectronic devices 106 so as to maximize the optical couplingbetween the optoelectronic devices 106 and the optical fibers 114, whichare packaged in the first ferrule 112. The spacer may function to adjustthe length of the wire bonds or other electrical connection meansbetween the array of optoelectronic devices 106 and other componentssuch as the driver or amplifier chip 108. The spacer also may be used toaid in creating a gap between the array of optoelectronic devices 106and the array of optical fibers that are inside the first ferrule 114.

[0081] The spacer 314 also may function to raise the height of the arrayof optoelectronic devices 106 so that a top surface of the array ofoptoelectronic devices 106 is approximately on the same plane as theother components, such as the driver or amplifier chip 108, that areadapted on the head region 302, as shown in FIG. 3a or FIG. 3b.Advantageously, by maintaining the optoelectronic devices on the sameplane as the other electrical components, the wire bonds 312 between thecomponents on the head region 302 more robust and efficient.

[0082] The spacer 314 may be optional if the optoelectronic devices 102have sufficient height so as to place the second end of the firstferrule 320 at an optimal position above the top surface of the driveror amplifier chip 108. According to a preferred embodiment, a smallinterstitial space or gap is maintained between the second end of thefirst ferrule 320 and the top surface of the optoelectronic devices 102.In alternative embodiments, this interstitial gap may be omitted.

[0083] In another embodiment, the spacer 314 also may function to createor form a gap between the array of optoelectronic devices 106 and thearray of optical fibers. Specifically, the spacer 314 may be adjacent tothe array of optoelectronic devices. The top surface of the spacer 314may be higher than the top surface of the array of optoelectornicdevices 106. The top surface of the spacer may be in contact with thesecond end of the first ferrule 320. Accordingly, this creates or formsa gap between the optoelectronic devices and array of optical fiberspackaged in the first ferrule.

[0084] 5. Optoelectronic Mounting Structure

[0085] The electrical components on the flexible printed circuit board102 generate heat, and an optoelectronic mounting structure 702 may beused to transmit this heat to the circuit board mounting structure 104,as explained below.

[0086]FIG. 7a is a cut-away-side view showing an alternative embodimentof the head region 302 of the flexible printed circuit board 102,according to an embodiment of the invention. Specifically, theoptoelectronic mounting structure 702 has a first surface 710 and asecond surface 712. The first surface 710 of the optoelectronic mountingstructure 702 passes along a second surface 704 of the head region 302of the flexible printed circuit board 102. The second surface 712 of theoptoelectronic mounting structure 702 is adapted to an upper surface 708of the circuit board mounting structure 104 with a compliant adhesive.The optoelectronic mounting structure may be copper or a similarconductive material. The optoelectronic mounting structure may be coatedwith gold or other adhesion promotion layers such as nickel. An window706 may be formed in the head region 302 of the flexible printed circuitboard 102 so as to provide access to the optoelectronic mountingstructure 702. The array of optoelectronic devices 106 may be mounted inthe window 706 directly on top of the optoelectronic mounting structure702. Accordingly, the optoelectronic mounting structure provides athermal and an electrical contact area for the optoelectronic devices.Other electrical components, such as the driver or amplifier chip 108also may be mounted in the window 706 directly on the optoelectronicmounting structure 702.

[0087] The optoelectronc mounting structure advantageously 702dissipates heat generated by the array of optoelectronic devices 106 andother electrical components by spreading the heat and efficientlytransmitting it to the circuit board mounting structure 104. Theoptoelectronic mounting structure 702 also provides an electricalcontact path to the optoelectronic devices 106 since the back side ofthe optoelectronic devices 106 may be gold or copper plated and may bemounted directly to a copper optoelectronic mounting structure 702.Moreover, since the optoelectronic mounting structure 702 may be a solidcopper plane, it may acts to limit electromagnetic interference. Actingas a ground plane for the optoelectronic devices 106, the optoelectronicmounting structure 702 provides electrical shielding by containing anyelectrical fields that may exist so that the electrical fields do notradiate and create cross talk. The optoelectronic mounting structure 702additionally may provide a stable mounting surface for theoptoelectronic devices 106, and it may function to raise or change theheight of the electrical components. The optoelectronic mountingstructure 702 also provides mechanical rigidity to the head region 302of the flexible printed circuit board 102. This mechanical rigiditystiffens the head region 302 and advantageously aids in the assemblyprocess.

[0088]FIG. 7b is a cut-away-side view showing an alternative embodimentof the head region 302 of the flexible printed circuit board 102,according to an embodiment of the invention. Specifically, openings 714in the head region 302 of the flexible printed circuit 102 board mayfunction to dissipate heat to the optoelectronic mounting structure 702.The openings 714 may be heat pipes, thermal vias or similar structuresthat transmit heat. The openings 714 may be formed in the head region302 so as to provide access to the optoelectronic mounting structure702. Electrical components, such as the array of optoelectronic devices106 and the driver or amplifier chip 108, may be mounted on the firstsurface of the head region 302. Heat generated by these electricalcomponents may pass through the openings 714 and to the optoelectronicmounting structure 702. The optoelectronic mounting structure 702dissipates or spreads this heat to the circuit board mounting structure104.

[0089] 6. Ferrule

[0090] The optical module 100 may include the first ferrule 112, asshown in FIG. 3a or FIG. 3b. The first ferrule is mounted on the headregion 302 of the flexible printed circuit board 102. More specifically,the second end of the first ferrule 320 is mounted on the top surface ofthe array of optoelectronic devices 106. The first ferrule 112 isprecisely aligned and attached directly above the active region of thearray of optoelectronic devices 106 so that a high coupling efficiency(low loss of light) is achieved. In other words, each optical fiber 114in the first ferrule 112 is accurately aligned to a correspondingindividual optoelectronic device 106 so that the array of optical fibers114 inside the first ferrule 112 is optically aligned with the array ofoptoelectronic devices 106. The precise alignment and attachment of thefirst ferrule 112 to the array of optoelectronic devices 106 isaccomplished by using highly precise machinery and adhesive, and thisnovel process is explained below.

[0091] The first ferrule 112 may comprise a rectangular ferrule. Thefirst ferrule 112 packages an array of optical fibers 114, extendingfrom a first end 318 of the first ferrule 112 to a second end 320 of thefirst ferrule 112. Two alignment pins 316 may be adapted to the firstend 318 of the first ferrule 112. The alignment pins function to matethe first ferrule 112 to a second ferrule 206. Alternatively, twoalignment pin holes may be adapted to the first end 318 of the firstferrule 112 in place of the two alignment pins 318. The alignment pinholes function to mate the first ferrule 112 to a second ferrule 206.

[0092]FIG. 8 is a side-view showing an alternative embodiment of thefirst ferrule 112 and the head region 302 of the flexible printedcircuit board 102, according to an embodiment of the invention. Costsare reduced by using a smaller optoelectronic device 106, as shown inFIG. 8. A notch 802 exists at the second end of the first ferrule 320 sothat there is sufficient room for wire bonding between theoptoelectronic devices 106 and driver or amplifier chip 108.Advantageously, the notch 802 allows positioning the driver chip oramplifier chip 108 in close proximity to the smaller optoelectronicdevices 106. Therefore, the notch 802 obviates the need for long wirebonds to connect the optoelectronic devices to the driver or amplifierchip.

[0093] In another embodiment, an array of optical elements may be usedin place of the array of optical fibers 114. The optical element maycomprise a lenslet array, diffractive optic array, a lens, filter,pipette, capillary tube or optical fibers. Also, the optical elementdoes not have to be optical as, for example, in embodiments of thepresent invention in which biological or chemical analysis is performed.The optical element array may be a one-dimensional, two-dimensional ormulti-dimensional array of optical elements.

[0094] In contrast to a single optical element or fiber, an array ofoptical elements or fibers introduces engineering, design, assembly andpackaging complexity. This complexity was taken into account inembodiments of the invention. For example, an array of optical elementsgenerates more heat and electromagnetic interference that a singleoptical element, and this must be considered in all aspects of makingand using the device. Also, unlike aligning a single optical element toan optoelectronic device, aligning an array of optical elements to anarray of optoelectronic devices is considerably more difficult andcomplex. Moreover, an array of optical elements can more readily becomeeffected by electrical or optical cross-talk since the optical elementsare closely coupled. Therefore, the array is highly subject to signaldegradation, and design limitations must be made to take these factorsinto account. Additionally, working with an array rather than a singleoptical fiber requires developing new tools and techniques for variousmanufacturing aspects such as precision alignment and eye-safety. Suchtools and techniques were developed specifically for embodiments of thisinvention. In summary, for these and other reasons, an array of opticalelements introduces engineering, design, assembly and packagingcomplexity that is simply not present with a signal optical element, andthis added complexity was taken into account in embodiments of theinvention.

[0095] 7. First Adhesive

[0096] Prior to mounting the first ferrule 112 on top of the array ofoptoelectronic devices 106, a first adhesive 116 is dispensed on the topsurface of the array of optoelectronic devices 106, as shown in FIG. 3aor FIG. 3b. The first adhesive is preferably an optically clear adhesiveor a gel that has a complementary index of refraction to the opticalfibers 114.

[0097] The first ferrule 112 is held suspended above the top surface ofthe array of optoelectronic devices 106 in the first adhesive 116. Theoptical adhesive 116 may be cured with UV light, RF radiation, air,microwave radiation or thermal means, depending on the type of adhesivethat is used. Once the optical adhesive 116 is cured, the space or gapbetween the second end of the first ferrule 320 and the top surface ofthe optoelectronic devices 118 is preserved or set; this space havingbeen filled with the first adhesive 116. In other words, a thin layer offirst adhesive 116 exists at the interface between the second end of thefirst ferrule 320 and the top surface of the optoelectronic devices 118.

[0098] The first adhesive 116 functions to stabilize and hold the firstferrule 112 to the array of optoelectronic devices 106. The firstadhesive 116 maintains the precise alignment of the array of opticalfibers 114 packaged in the first ferrule 112 to the array ofoptoelectronic devices 106. The first adhesive also functions tomaintain the gap that exists between the first ferrule 112 and array ofoptoelectronic devices 106.

[0099] Advantageously, the first adhesive 116 produces a high couplingefficiency between the array of optical fibers 114 packaged in the firstferrule 112 and the array of optoelectronic devices 106. Specifically,the first adhesive 116 is an optically clear adhesive or gel and hasalmost the same refractive index as the optical fibers. Accordingly, byproviding a refractive index match to the optical fibers, light passingfrom the array of optoelectronic devices 106 to the array of firstfibers 114 (or vice versa) experiences minimal Fresnel reflection lossand optical divergence over the gap distance that exists between thearray of optoelectronic devices 106 and the array of first fibers 114.This produces a high-coupling efficiency at the interface between thetop surface of the optoelectronic devices 106 and the optical fibers114. The first adhesive 116 also serves to prevent air from existing atthe interface or space between the first ferrule 112 and the array ofoptoelectronic devices 106. The elimination of air at the interface orgap is desirable because air has a lower refractive index than theoptoelectronic devices 106, the optical fibers 114 and the firstadhesive 116. The refractive index difference introduces reflectionlosses, and the lower reflective index results in greater beamdivergence per unit propagation length. If air were present, lightpassing from the optoelectronic devices 106 to the optical fibers 114(or vice versa) may experience greater divergence, thereby reducing theefficiency of the coupling. Furthermore, the first adhesive prevents asecond adhesive 122 from inadvertently seeping or wicking into the gapor space between the bottom surface of the ferrule and the top surfaceof the optoelectronic devices. Consequently, the first adhesive 116advantageously produces a high-coupling efficiency between theoptoelectronic devices 106 and the optical fibers 114 that are packagedin the first ferrule 112.

[0100] The first adhesive 116 not only enhances the coupling efficiencybetween the optical fibers 114 and optoelectronic devices 106 byproviding a refractive index match to the optical radiation, but it alsoserves another important purpose. Specifically, the first adhesive 116provides mechanical robustness by securing the first ferrule 112 to thearray of optoelectronic devices 106. As previously stated, the gap orspace between the bottom surface of the first ferrule 112 and the topsurface of the optoelectronic devices 118 is filled with the firstadhesive. The first adhesive functions to mechanically stabilize thefirst ferrule 112 to the head region 302 of the flexible printed circuitboard 102. The first adhesive 116 provides support for any lateral,axial or rotational strain that may be created when a fiber optic cableis attached to the optical module. Furthermore, this allows proceedingto the dam and well-fill step, which is explained below, with minimal orno supporting structure to maintain the precision axial alignment of thearray of optical fibers 114 packaged in the first ferrule 112 to thearray of optoelectronic devices 106. Accordingly, the first adhesive 116advantageously reduces manufacturing time and costs by providingmechanical robustness in addition to providing high coupling efficiency.

[0101] 8. Second Adhesive and Dam

[0102] As previously stated, the first adhesive mechanically stabilizesthe first ferrule 112 to the head region 302 of the flexible printedcircuit board 102. In another embodiment, a second adhesive 122 may beadapted to the head region 302 to further mechanically stabilizes thefirst ferrule 112 to the head region 302 of the flexible printed circuitboard 102, as shown in FIG. 3a or FIG. 3b. Similar to the first adhesive116, the second adhesive 122 may provide support for any lateral, axialor rotational strain that may be created when a fiber optic cable isattached to the optical module. No dam is necessary to form the firstadhesive 116.

[0103] To further mechanically stabilize the first ferrule 112 to thehead region, a dam 120 may be formed on the head region 302 and filledwith the second adhesive 122, as shown in FIG. 3a or FIG. 3b. The secondadhesive, however, may be used without the dam. The dam may beconstructed or dispensed, and the dam 120 may be dispensed and formed ina single or multi-layered path. The dam 120 may be in the shape of asquare, diamond, oval or any other shape that effectively stabilizes andencloses the optoelectronic devices and possibly wire bonds and otherdie on the head region 302 of the flexible printed circuit board 102.The dam 120 may furthermore surround and enclose all of the componentson the head region 302 for extra protection. The dam 120 may beconstructed and formed on the first surface 310 of the head region 302of the flexible printed circuit board 102.

[0104] The dam 120 may surround the first ferrule 112, driver oramplifier chip 108 or other electrical components, as shown in FIG. 3aor FIG. 3b. The dam 120 may be composed of adhesive or epoxy. The dam120 may be formed or built by dispensing several layers of adhesive orepoxy on top of each other over time until the desired height and widthof the dam 120 is achieved. The adhesive or epoxy may be any standardwell-fill or potting epoxy. Alternatively, as previously stated, the dammay be dispensed and formed in a single path.

[0105] The area within the dam may be filled with the second adhesive122. The second adhesive 122 preferably covers the driver or amplifierchip 108, array of optoelectronic devices 106, and any other electricalcomponents that are adapted to the head region 302, as shown in FIG. 3aor FIG. 3b. A sufficient amount of second adhesive 122 is poured insidethe dam area so that the height of the second adhesive 122 may span fromthe first surface 310 of the head region 302 of the flexible printedcircuit board 102 to somewhere below the first end 318 of the firstferrule 112, as shown in FIG. 3a or FIG. 3b. After the second adhesive122 has been cured, the dam 120 and second adhesive 122 function tomechanically stabilize the first ferrule 112 to the first surface 310 ofthe head region 302 of the flexible printed circuit board 102.

[0106] Advantageously, the dam 120 and second adhesive 122 may provideadditional mechanical support to further stabilize the first ferrule 112to the head region 302 of the flexible printed circuit board 102. Thedam 120 and second adhesive 122 may function to absorb stress andprovide rigidity and strength that may be needed when connecting theoptical module to an external environment such as a fiber optic cable.Also, the dam 120 and second adhesive 122 may prevent movement that mayoccur over temperature variances. Moreover, the dam 120 and secondadhesive 122 may function to provide moisture blocking and protection tothe electrical components and circuitry adapted to the first surface 310of the head region 302 of the flexible printed circuit board 102.

[0107] 9. Third Layer

[0108] For airtight sealing of the optical module, the surface area ofthe second adhesive 122 may be covered with a third layer. The thirdlayer may protect the optical module by blocking the permeation ofmoisture and providing electric shielding. The third layer may be aconductive and or moisture blocking adhesive such as gel silicon resin.It may also be a metallic, dielectric or other type of coating thatprovides necessary protection to the optical module.

[0109] 10. Attenuator or Conditioner

[0110] In an embodiment of the invention, an attenuator may be used thatfunctions to modify the performance of the array of optoelectronicdevices. Specifically, superior performance of the array ofoptoelectronic devices typically is found if such devices are operatedat the midpoint rather than low-point of their power range. However,operating the optoelectronic devices at the mid-point of their powerrange may not meet optical output requirements. One solution is tooperate the optoelectronic devices at the mid-point of their power rangebut not transmit all of the power out of the end of the array of opticalfibers. This may be accomplished through the use of the attenuator. Theattenuator may function to reflect, absorb and or scatter the opticaloutput of at least one optoelectronic device. Also, the attenuatoradvantageously may control optical cross-talk, reduce back-reflectionand may eliminate feedback noise.

[0111] One embodiment of the attenuator may be a coating on the first orsecond end of the first ferrule or a coating on the first or second endof the array of optical elements that are packaged in the ferrule. Italso may comprise a coating on the first end of the array ofoptoelectronic devices. The coating may be a metal, dialetric, organicor other material, and the coating may be patterned. Another embodimentof the attenuator may be a gel-like substance that is deposited in thegap that exists between the first end of the optoelectronic devices andthe first end of the optical fibers. In this embodiment, the attenuatorwould function to absorb some of the light emitted by the optoelectronicdevices. Other embodiments of the attenuator may be increasing theabsorption of the first adhesive, introducing a controlled seeping orwicking of an absorbing second adhesive, changing the gap distance toreduce coupling, changing the refractive index to introduce Fresnelreflection and introduce divergence, changing the lateral alignment, orchanging the surface finish of the optical fibers. Finally, otherembodiments of the attenuator may include changing the opticaltransmission characteristics of the array of optical fibers so that theyabsorb, reflect and or scatter light. In this manner, the optical energyexiting the array of optical fibers will have its signal power reduced.This may be accomplished by changing the surface finish of the cores ofthe optical fibers (e.g., using frosted, wavy or rough surface glass) orby coating the inner surfaces of the fiber optic cores.

[0112] Finally, in another embodiment of the invention, a conditionermay be used to improve the performance of the array of optical fibers bychanging the way the optical energy is launched into the optical fibers.For example, conditioning the launch of optical energy can improve theeffective bandwidth of the optical fibers. The conditioner may functionto change the phase distribution of the optical energy that is emittedby the optoelectronic devices.

[0113] Conditioning the launch of the optical energy flowing into theoptical fibers from the optoelectronic devices may be accomplished asfollows: (1) patterning a coating on the first end of the array ofoptoelectronic devices; (2) patterning a coating on the first or secondend of the array of optical fibers; (3) depositing a gel-like substancebetween the first end of the optoelectronic devices and the first end ofthe optical fibers; (4) adapting a diffractive object on the input oroutput of the array of optical fibers so as to change the structure ofthe optical energy; (5) changing the lateral position of the array ofoptoelectronic devices relative to the array of optical fibers; (6)changing the optical transmission characteristics of the array ofoptical fibers; (7) tilting the array of optoelectronic devices relativeto an optical path; and (8) changing the optical transmissioncharacteristics of the array of optical fibers so that they absorb,reflect and or scatter light. These and other methods that are known inthe art may be used to improve the performance of the array of opticalfibers by changing the way the optical energy is launched into theoptical fibers.

[0114] B. Buckle Region

[0115] In addition to the head region 302, the flexible printed circuitboard 102 also comprises a buckle region 304, which will now bedescribed with reference to FIG. 3a or FIG. 3b. The buckle region 304 isthat area of the flexible printed circuit board 102 connecting the headregion 302 to the main body region 306 of the flexible printed circuitboard 102. The buckle region 304 is thin and composed of the samemulti-layered structure as the other regions of the flexible printedcircuit board 102. A plurality of electrical circuitry may be adaptedboth to a first surface and a second surface of the buckle region 304.The electrical circuitry functions to electrically connect the headregion 302 to the main body region 306 of the flexible printed circuitboard 102.

[0116] The buckle region functions to absorb any stress and misalignmentthat may occur when the head region 302 and main body region 306 areconnected to the circuit board mounting structure 104 during theassembly process. Specifically, after the head region 302 is attached tothe circuit board mounting structure 104, the flexible printed circuitboard 102 is wrapped or folded around and attached to the circuit boardmounting structure 104, as explained in detail below. Alternatively, themain body region 306 may be first connected to the circuit boardmounting structure 104 followed by folding the flexible printed circuitboard and connecting its head region 302 to the circuit board mountingstructure 104. The housing 124 is then connected to the circuit boardmounting structure 102. The first ferrule 112, which is adapted to andprotrudes from the head region, is then aligned and housed in alongitudinal cavity 1006 of the housing 124. However, stress ormisalignment may occur when connecting the housing 124 to the circuitboard mounting structure 104.

[0117] The buckle region 304 functions to absorb any misalignment orstress that may occur during this assembly process. As shown in FIG. 3aor FIG. 3b, the buckle region 304 bends in the “Y” direction. Bendingthe buckle region 304 provides the buckle region 304 with bendingfreedom in the x, y and z direction, as well as rotational freedom. Thisbending freedom allows the buckle region 304 to absorb any stress thatmay occur during the assembly process when aligning and attaching thehousing 124 to the circuit board mounting structure 104.

[0118] C. Main Body Region

[0119] In addition to a buckle region 304 and a head region 302, theflexible printed circuit board 102 also comprises a main body region306. The main body region 306 will now be described with reference toFIG. 3a or FIG. 3b. The main body region 306 is thin, rectangular shapedand flexible. The main body region 306 is composed of the samemulti-layered structure as the other regions of the flexible printedcircuit board. The main body region 306 functions to house the otherelectrical components and circuitry of the optical module 100. Theelectrical components may serve a variety of functions, includingconnection of the optical module to the system to which it is located.Accordingly, a plurality of electrical components 308 and a plurality ofelectrical circuitry may be adapted to a first surface 324 and/or asecond surface 326 of the main body region 306 of the flexible printedcircuit board 102, as shown in FIG. 3a or FIG. 3b.

[0120] 1. Electrical Connections

[0121] A series of electrical connections may be adapted to the first orsecond surface 324 of the main body region 324 of the flexible printedcircuit board 102. The electrical connections function to electricallyconnect the flexible printed circuit board to an external environmentsuch as another circuit board. The electrical connections may compriseball grid arrays, solder balls, wire leads, land-grid arrays withconductive interposers, or any other means to electrically connect theflexible printed circuit board to an external environment.

[0122] D. Summary

[0123] In summary, the flexible printed circuit board 102 supports themain electrical components and elements of the optical module, such asthe optoelectronic devices 106, driver or amplifier chip 108 and firstferrule 112, as well as providing bending freedom and stress relief tothe optical module 100. The flexible printed circuit board 102 isattached to, and partially enclosed by, a housing 902, which isdescribed below.

[0124] II. Circuit Board Mounting Structure and Housing

[0125]FIG. 9 is an exploded view of the flexible printed circuit board102, first ferrule 112, a circuit board mounting structure 104 and anhousing 124.

[0126] A. Circuit Board Mounting Structure

[0127] The circuit board mounting structure 104 functions in part as amounting structure for the flexible printed circuit board and as a heatsink to dissipate heat generated by the circuit board 102. Specifically,the flexible printed circuit board 102 is bent and wrapped around thecircuit board mounting structure 104. A second surface 904 of theflexible printed circuit board 102 is attached to a bottom surface 914and a first end 910 of the circuit board mounting structure 104, asshown in FIG. 9. Alignment ridges, guide pins or guide pin holes mayexist along the bottom surface 914 and first end 910 of the circuitboard mounting structure, although they are not necessary. The alignmentfeatures assist in aligning and holding the flexible printed circuit 102board to the circuit board mounting structure. A fourth adhesive is usedto firmly attach the flexible printed circuit board 102 to the circuitboard mounting structure 104. The thermal expansion coefficient andcompliance of the fourth adhesive advantageously assists in preventingexpansion or contraction of the circuit board mounting structure fromdamaging the flexible printed circuit board 102. The flexible printedcircuit board 102 bends around the circuit board mounting structure 104in such a manner that the head region 302 of the flexible printedcircuit board 102 is housed inside the first end 910 of the circuitboard mounting structure 104, as shown in FIG. 9. A cavity 912 on thefirst end 910 of the circuit board mounting structure 104 functions tohouse the head region 302 of the flexible printed circuit board 102. Inanother embodiment, there is no cavity 912, as explained below. A seriesof heat sink ridges adapted to the circuit board mounting structurefunction to dissipate heat generated by the flexible printed circuitboard.

[0128] In an embodiment as shown in FIG. 7, the second surface 704 ofthe head region 302 of the flexible printed circuit board 102 isattached to the first surface 710 of the optoelectronic mountingstructure 702. The second surface 712 of the optoelectronic mountingstructure 702 is attached to the upper surface 708 of the circuit boardmounting structure 104 with a compliant adhesive. The flexible printedcircuit board 102 then wraps around the circuit board mounting structure104 so that the remaining portion of the second surface 904 of theflexible printed circuit board is attached to the bottom surface 914 ofthe circuit board mounting structure 104, as shown in FIG. 9.

[0129] As shown in FIG. 9, the circuit board mounting structure has feet916 for connecting the optical module 100 to an external environmentsuch as a second circuit board 202. The feet 916 have ridges that allowa portion of each foot 916 to drop into a hole on the second circuitboard 202 and therefore attach and align the optical module 100 to thesecond circuit board 202. The ridges on the feet also maintain theoptical module 100 at a specified distance above the second circuitboard 202.

[0130] The circuit board mounting structure 104 has snap slots 906, setscrew holes and or alignment pin holes on the first end 910 forconnecting the first end of the circuit board mounting structure tohousing 124, as discussed in detail below.

[0131] B. Housing

[0132] The housing 124 is connected to the circuit board mountingstructure 104, and the housing 124 will now be described in detail withreference to FIG. 10. The housing 124 may be made of a non-conductivematerial. The housing 124 comprises a mating end 1002, as shown in FIG.10a, and a receiving end 1004, as shown in FIG. lob. A longitudinalcavity 1006 extends through the housing 124 from the mating end 1002 tothe receiving end 1004, as shown in FIGS. 10a-10 b.

[0133] The mating end 1002 of the housing 124 has tabs 1008 andalignment pins 1010 for connecting the mating end 1002 to the first end910 of the circuit board mounting structure 104, as shown in FIG. 10a.The position of the tabs 1008 correspond to the position of the snapslots 906 located on the first end 910 of the circuit board mountingstructure 104. Similarly, the position of the alignment pins 1010correspond to the position of the alignment pin holes on the first end910 of the circuit board mounting structure 104. (See FIG. 9.) Thus, bysimply engaging the tabs 1008 and alignment pins 1010 on the housing 124into the snap slots 906 and alignment pin holes on the circuit boardmounting structure 104, the housing 124 snaps on to the circuit boardmounting structure 104 and is firmly attached. In the above-statedembodiment, the housing is snapped onto the circuit board mountingstructure. In other embodiments, the housing may be connected by usingother attachment methods such as glue, screws or through the use ofother mechanical fixtures. Furthermore, inserts may be adapted to themating end of the housing that function to hold the circuit boardmounting structure to the housing. The inserts aid in applying a forceto the tabs that maintain the tabs firmly in place. These inserts may bein the form of wedges, spring-clips, stakes or shims.

[0134] Additionally, alignment members on the mating and receiving endsof the housing function to hold and align the position of the first andsecond ferrules relative to the position of the housing. These alignmentmembers may be inwardly sloping walls at an opening of the longitudinalcavity. The alignment members act independently or in concert with thealignment pins and tabs to align and connect the first ferrule and thecircuit board mounting structure.

[0135] Once the housing 124 is snapped onto the circuit board mountingstructure 104, at least one elastomeric pressure ring 1012 that is inproximity to the housing 124 functions to secure the housing 124 and thehead region 302 of the flexible printed circuit board 102 to the circuitboard mounting structure 104. Specifically, the elastomeric pressurering 1012 may be in a variety of shapes and forms such as a circular,oval spaces or donuts, as shown in FIG. 9. The elastomeric pressure ring1012 has multiple purposes. First, upon connecting the housing 124 tothe circuit board mounting structure 104, the elastomeric pressure ring1012 is compressed, and this compression creates an outward elastomericforce in the direction of the receiving end 1004 of the housing 124 thatmaintains the tabs 1008 and the snap slots 906 in a firmly lockedposition. With the compression force on the tabs 1008 and snap slots906, a high degree of manufacturing tolerances is achieved. Second, thepressure or force created by the compressed ring 1012 aids in bondingthe optoelectronic mounting structure 702 to the circuit board mountingstructure 104. The optoelectronic mounting structure 702 is bonded tothe circuit board mounting structure 104 with adhesive, and the pressureproduced by the compressed ring 1012 holds the optoelectronic mountingstructure 702 firmly against the circuit board mounting structure 104while the adhesive is cured. Accordingly, the elastomeric pressure ring1012 produces tighter bonding between the circuit board mountingstructure 104 and the optoelectronic mounting structure 702. Third, oncethe housing 124 is snapped onto the circuit board mounting structure104, the pressure or force created by the elastomeric pressure ring 1012provides a more robust moisture seal between the housing 124 and thecircuit board mounting structure 104.

[0136] Upon attachment of the housing 124 to the circuit board mountingstructure 104, the first ferrule 112 is housed in the longitudinalcavity 1006 of the housing 124, and alignment ridges inside thelongitudinal cavity 1006 engage and hold the first ferrule 112 in place.

[0137] In the above-described embodiment as shown in FIGS. 9-10, thehousing 124 slides into the circuit board mounting structure 104, andthe head region 302 of the flexible printed circuit board 102 is buriedin the cavity 912 of the first end 910 of the circuit board mountingstructure 104. However, in another embodiment, the first end 910 of thecircuit board mounting structure 104 may not have a cavity, and the headregion 302 may exist on the outside of the first end 910 of the circuitboard mounting structure 104. In this embodiment, instead of having thehousing 124 slide into the circuit board mounting structure 104, thehousing 124 may slide over the circuit board mounting structure 104, andthe head region 302 may be housed in a cavity inside the housing 124. Instill another embodiment, neither the housing 124 nor the circuit boardmounting structure 104 may have a cavity, and the two parts simply maymate with each other.

[0138] Finally, in another embodiment of the housing, a metallic coatingmay be applied to at least a portion of the mating end 1002 of thehousing 124. The metallic coating functions to provide electromagneticshielding. In yet another embodiment, the housing may be made out ofmultiple materials and at least one of those materials would function toprovide electromagnetic shielding.

[0139] C. Attachment of Fiber Optic Cable

[0140] Finally, as shown in FIG. 10b, the receiving end 1004 of thehousing 124 functions to connect the optical module 100 to an externalsystem. The receiving end 1004 receives a second ferrule 206, which istypically attached to one end of a fiber optic cable 204. The secondferrule mates with the first ferrule, as described below. The secondferrule 206 may be a MT type connector, MU type connector, MPO typeconnector or other type connectors.

[0141] In operation, the second ferrule 206 is inserted into thereceiving end 1004 of the housing 124. Wings 1014, snaps or beams on thereceiving end 1004 align, grab and hold the second ferrule 206, and thewings 1014 snap onto the second ferrule 206. The wings 1014 function toprovide alignment compliance when connecting the second ferrule 206 tothe housing 124. Moreover, the wings 1014 are flexible and may absorbany stress that may arise due to movement of the cable 204 that isattached to the second ferrule 206. The wings 1014 further provide aholding force that aids in holding the second ferrule 206 to the firstferrule 112. Alignment ridges inside the longitudinal cavity 1006 of thehousing 124 further engage and hold the second ferrule 206 in place.

[0142] Once inside the longitudinal cavity 1006, the second ferrule 206mates with the first ferrule 112 that is also housed in the longitudinalcavity 1006 of the housing 124. The second ferrule 206 mates with thefirst ferrule 112 by engaging the alignment pins 316 located on thefirst end 318 of the first ferrule 112 with alignment pin holes locatedon a mating end of the second ferrule 206. The alignment pins 316 andalignment pin holes function to provide fine alignment between themating arrays of optical fibers that are packaged within the matingferrules. Alternatively, the first ferrule may have alignment holes andthe second ferrule may have alignment pins, and the ferrules wouldaccordingly mate in a similar fashion.

[0143] Once the ferrules are mated, the array of optical fibers that arepackaged in the ferrules are axially aligned, and the ferrules areoptically connected. For example, if the optical module 100 functions asa receiver, optical signals pass from the fiber optic cable 204, throughthe optical fibers packaged in the ferrules 206 and 112 and to theoptoelectronic devices 106, which are mounted on the flexible printedcircuit board 102. The optical module 100 converts the optical signalsinto electrical signals and transmits these signals to an externalenvironment, such as a printed circuit board, for processing.

[0144] III. Alignment and Attachment Process

[0145] A. Overview

[0146] An important aspect of an embodiment of the invention is theprecise alignment and attachment of the first ferrule 112 to the arrayof optoelectronic devices 106 that are mounted on the flexible printedcircuit board 102. A process, according to an embodiment of theinvention, for aligning and connecting the first ferrule 112 to thearray of optoelectronic devices 106 comprises the following steps:

[0147] 1. Holding the first ferrule 112 directly above theoptoelectronic devices 106;

[0148] 2. Aligning the array of optical fibers 114 packaged in the firstferrule 112 with the array of optoelectronic devices 106 so that eachoptical fiber is optically aligned to a corresponding individualoptoelectronic device;

[0149] 3. Depositing the first adhesive 116 on a top surface of thearray of optoelectronic devices 106;

[0150] 4. Placing the first ferrule 112 on top of the first adhesive116;

[0151] 5. Tacking and curing the first adhesive 116 as to mechanicallystabilize the first ferrule 112; and

[0152] 6. Forming a dam 120 around the first ferrule 112 on the flexibleprinted circuit board 102, dispensing the second adhesive 122 inside thedam area, and curing the first adhesive 122.

[0153] These precision alignment and attachment steps are discussedbelow.

[0154] A high-precision alignment machine may be used in combinationwith a series of other apparatuses to produce precise alignment andattachment of optical fibers to optoelectronic devices. These machinescombine many critical technologies to perform alignment with a low-costmanufacturing environment. These technologies include: (1) ahigh-precision stage that is used to hold the flexible printed circuitboard 102; (2) a high-precision alignment arm for accurately placing thefirst ferrule 112 on the optoelectronic devices 106 that are adapted tothe flexible printed circuit board 102; (3) a top-down view camera; (4)side-view camera; (5) video monitors; (6) split-field microscope; and(7) optical video system function together to replace thelabor-intensive active-alignment process. Alternatively, computers andsoftware may perform many of above-stated technologies. An example ofone of the many process that may be used with this equipment isexplained in the following paragraphs.

[0155] B. An Apparatus for Holding an Optical Element

[0156] The first step in the precise alignment and attachment of thefirst ferrule 112 to the array of optoelectronic devices 106 is to holdthe first ferrule 112 at the end of a high-precision stage. This isaccomplished through the use of an apparatus for holding an opticalelement, as explained in this section.

[0157]FIGS. 11a-11 b show views of an embodiment of the apparatus forholding an optical element. The apparatus for holding an optical element1100 holds the first ferrule 112 through the use of pin-positioningholes 1102 and vacuum pressure. The apparatus for holding an opticalelement has a first end 1112 and a second end 1114. The apparatus forholding an optical element 1100 may have two pin-positioning holes 1102on a bottom surface 1104 of the second end 1114 for receiving thealignment pins 316 of the first ferrule 112, as shown in FIGS. 11a-11 b.As shown in FIG. 11b, an array of optical fibers 1106 may be packagedbetween the pin-positioning holes 1102, and it is optically aligned withthe array of optical fibers 114 that are packaged in the first ferrule112. The innermost optical fibers in the apparatus for holding anoptical element 1100 are milled out, forming a longitudinal cavity 1108running through the apparatus for holding an optical element 1100 fromthe first end 1112 to the second end 1114, as shown FIG. 11b. A vacuumis placed at a top surface of the first end 1112 of the longitudinalcavity 1108, and the longitudinal cavity 1108 functions as a vacuumslot. Accordingly, once the alignment pins 316 from the first ferrule112 are mated with the pin-positioning holes 1102 on the apparatus forholding an optical element 1100, the vacuum slot functions as a vacuumclamp, holding the first ferrule 112 in place. Alternatively, anelectrostatic clamp may be used in place of the vacuum clamp. Also,another embodiment may comprise alignment pins in place of thepin-positioning holes 1102, and the alignment pins would function toconnect to pin-positioning holes in a ferrule.

[0158] The apparatus for holding an optical element 1100 has multipleadvantages and uses. First, it permits holding and manipulating thefirst ferrule 112 in both the x, y, and z direction as well asrotational directions. This aids in achieving precise alignment andattachment of the first ferrule 112 to the optoelectronic devices 106.Also, the apparatus for holding an optical element 1100 grasps the firstferrule 112 without interfering, obscuring or damaging the opticalfibers 114 in the first ferrule 112. Additionally, the apparatus forholding an optical element 1100 allows access to the optical fibers 114in the first ferrule 112 so that optical coupling may be achieved. Forexample, a light may be mounted on top of the apparatus for holding anoptical element 1100 so that the optical fibers 114 emit light whilebeing held by the apparatus for holding an optical element 1100. Thelight emitted from the fibers 114 may then be used to aid in opticallycoupling the first ferrule 112 to the optoelectronic devices 106.Conversely, light from the optoelectronic devices may be used to aid inoptically coupling the first ferrule 112 to the optoelectronic devices106. Additionally, the apparatus for holding an optical element 1100provides a strain-less release mechanism through the use of the vacuumclamp. By simply turning off the vacuum pressure, the apparatus forholding an optical element 1100 gently releases the first ferrule 112.

[0159] The apparatus for holding an optical element 1100 also may beused for a variety of different purposes other than holding a ferrule.For example, it may be used to align and attach a micro-pipette array toa biological sensor array or a lens array to a MEMS modulator array. Italso may be used to attach a single or array of optical fibers to avariety of different objects or devices. Moreover, the optical elementmay be a MT type connector, ferrule, MT-like ferrule, lenslet array, adiffractive optical element or any other type of device that may bealigned with the device. Accordingly, the apparatus for holding anoptical element 1100 has multiple advantages and uses.

[0160] C. Alignment Process—X, Y and Rotational Directions

[0161] Once the first ferrule 112 is held at the end of the highprecision arm by the apparatus for holding an optical element 1100, thenext step is to align the optical fibers with the optoelectronic devicesin the x, y and rotational directions. In this section, three differentalignment process are described.

[0162] 1. Image Alignment Process

[0163] The first process for aligning the optical fibers with theoptoelectronic devices in the x, y and rotational directions is an imagealignment process. In this embodiment of the invention, a split-fieldmicroscope is used to align the optical fibers with the optoelectronicdevices by super-imposing an image of at least one optical fiber with animage of at least one optoelctronic devices. Specifically, once thefirst ferrule 112 is held at the end of the high precision arm by theapparatus for holding an optical element 1100, the array ofoptoelectronic devices, which are mounted on a flexible printed circuitboard, are held on a high-precision stage. A top-down view camera may bemounted above the high-precision stage holding the optoelectronicdevices. With the aid of a split-view microscope and a split-field opticvideo system, a top-down image of the flexible printed circuit board102, situated on the high precision stage, is displayed on a monitor.

[0164] The focus and zoom on the split-field microscope and or the stageholding the flexible printed circuit board are adjusted until theoptoelectronic devices 106 that are adapted to the flexible printedcircuit board 102 are in view on the video monitor. The top surface ofthe array of optoelectronic devices 106 appears as rings 1202 on thevideo monitor under the high magnification of the microscope, as shownin FIG. 12a. A split-field video system permits simultaneous viewing oftwo opposite corners 1204 or ends of the array of optoelectronic devices106 with high magnification on the video monitor. The precision stageholding the flexible printed circuit board is adjusted until the firstoptoelectronic device 1206 and the twelfth optoelectronic device 1208are displayed simultaneously on the video monitor, as shown in FIG. 12b.

[0165] A light is mounted above the high-precision arm, emitting opticalradiation down into the optical fibers 114 that are packaged in thefirst ferrule 112. The light flowing down the optical fibers back-lightsthe fiber cores, and this provides a well-resolved image of the fibercores under the split-field microscope. The image of the cores thenappear as an array of well-resolved spots under the split fieldmicroscope, as shown in FIG. 12c.

[0166] Once the split-field microscope has formed an image of the fibercores and an image of the optoelectronic devices, these two images arethen superimposed by the split-field microscope to perform the alignmentprocess. Specifically, by adjusting the x and y position of thehigh-precision stage, the image of the illuminated fiber cores of thefirst optical fiber 1212 and twelfth optical fiber 1214 are alignedwithin the image of the rings of the first optoelectronic device 1206and twelfth optoelectronic device 1208 via the split-field microscope sothat the spots and rings form a bull's eye pattern, as shown in FIG.12d. This process precisely aligns in the x, y and rotational directionthe array of optical fibers 114 that are packaged in the first ferrule112 with the array of optoelectronic devices 106 that are adapted to theflexible printed circuit board 102. In another embodiment, images of theoptical fibers and optoelectronic devices other than the images of thefirst and twelfth optical fibers and optoelectronic devices may be usedto achieve the same result.

[0167] 2. Optical Energy Alignment Process

[0168] A second process to align the optical fibers with theoptoelectronic devices in the x, y and rotational directions is anoptical energy alignment process. In this embodiment of the invention,the flexible printed circuit board is again held by a high-precisionstage. A light is mounted above the high-precision arm that holds thefirst ferrule, and the light emits optical radiation down into theoptical fibers 114 that are packaged in the first ferrule 112. The lightflowing out of the optical fibers 114 radiates down onto the flexibleprinted circuit board 102, which is positioned on the high-precisionalignment stage. Under the high magnification of a microscope, thislight appears as a series of illuminating spots on the optoelectronicdevices 106. Each illuminating spot corresponds to an optical fiber inthe array of optical fibers 114 that are packaged in the first ferrule112. By adjusting the x and y position of the high-precision stage, thespots may be visually aligned with the rings to form a bull's eyepattern under the high magnification of a microscope. (This alignmentprocess may be performed by machine vision rather than by human vision.)The alignment process precisely aligns in the x, y and rotationaldirection the array of optical fibers 114 that are packaged in the firstferrule 112 with the array of optoelectronic devices 106 that areadapted to the flexible printed circuit board 102.

[0169] 3. Precision Placement Alignment System

[0170] A third process to align the optical fibers with theoptoelectronic devices in the X, Y and rotational directions is aprecision placement system. In this embodiment of the invention, aprecision placement system is connected to a high-precision arm thatholds the first ferrule, and the system also is connected to ahigh-precision stage that holds the optoelectronic devices. Theprecision placement system aligns the objects by first calculating theirinitial position in space by comparing their position to a knownposition in space. Based upon this information, the system calculatesthe relative distances that the objects are apart. Once the relativedistances are determined, the precision placement system aligns theobjects by sequentially moving the objects and re-calculating theirrelative distances until they are precisely aligned.

[0171] In one embodiment of the invention, the precision placementsystem may determine the initial position in space of the array ofoptical fibers and the optoelectronic devices by holding the objectswithin a field of view of a microscope. Since the position of thecross-hairs on the microscope is known, the precision placement systemknows the position of the optical fibers and optoelectronic devicesrelative to the position of the cross-hairs. Based upon thisinformation, the precision placement system then calculates the relativepositions of the objects to each other. Knowing the relative distances,the precision placement sequentially and continually moves the positionof the objects and re-calculates their relative positions to each otheruntil the optical fibers and optoelectronic devices are preciselyaligned.

[0172] In another embodiment of the invention, the precision placementsystem may determine the initial position in space of the array ofoptical fibers and the optoelectronic devices by moving the objects to apoint in space whose position is already known by the system. Forexample, the system may move the objects to corner mark on a jig or aprecision touch sensor. Once the objects are referenced to that point inspace, the precision placement system can calculate their relativepositions to each other. The precision placement system thensequentially moves the position of the objects while continuallyre-calculating their relative positions to each other until they areprecisely aligned.

[0173] D. Alignment Process—Z Axis Direction

[0174] Once the optical fibers 114 and optoelectronic devices 106 arealigned the X, Y and rotational directions, the high-precision alignmentarm is lowered until the first ferrule 112 is within a few microns fromthe optoelectronic devices 106. This vertical or Z-axis alignmentprocess is accomplished through the use of a video-image measuringsystem that functions in concert with the previously-described precisionequipment. This z-axis alignment process is described below.

[0175] A video-image measuring system is connected between a monitor anda side-view camera that is mounted near the side of the high-precisionstage. With the aid of the microscope, the side-view camera views theside of the optoelectronic devices 106 and first ferrule 112, and thisimage is displayed on the monitor.

[0176]FIG. 13 is a view of the monitor when using the video-imagemeasuring system. The video image measurement system generatespositional measuring lines 1302 over the images on the monitor, and thelines 1302 allow a user to measure the vertical distance or Z-axisheight between a bottom edge 1304 of the first ferrule 112 and a topedge 1306 of the optoelectronic devices 106, as shown in FIG. 13. Byadjusting the z position of the high-precision arm and thehigh-precision stage, the distance between the bottom edge 1304 of thefirst ferrule 112 to the top edge 1306 of the optoelectronic devices 106is adjusted until the objects are within a few microns (e.g.,approximately 35 microns apart). Accordingly, a gap exists between thefirst ferrule 112 and the optoelectronic devices 106.

[0177] In another embodiment of the process, the z-axis alignmentprocess may be accomplished by using laser-triangulation, interferencemicroscophy or a touch sensor.

[0178] E. Mechanical Stabilization Process

[0179] After the first ferrule 112 and optoelectronic devices 106 areprecisely positioned in space, the high-precision placement arm israised, moving the first ferrule 112 away from the optoelectronicdevices 106 in the vertical or Z-axis direction. A small volume of firstadhesive 116 is then dispensed on the top surface of the optoelectronicdevices 106 by a high precision, motor-driven syringe.

[0180] The high-precision placement arm is again lowered in the verticalor Z-axis direction until the first ferrule 112 contacts the opticaladhesive 116, which has been dispensed on the top surface of theoptoelectronic devices 106. The first ferrule 112 is suspended above thetop surface of the optoelectronic devices in the liquid optical adhesive116. The first adhesive 116 may be cured using a UV light curing system.

[0181] At this point, the first ferrule 112 is attached to theoptoelectronic devices 106 with the first adhesive 116 and is held fromabove by the apparatus for holding an optical element 1100. Aspreviously stated, the first adhesive mechanically stabilizes the firstferrule 112 to the optoelectronic devices 106. The first ferrule 112 isseparated from the apparatus for holding an optical element 1100releasing the vacuum clamp on the apparatus for holding an opticalelement 1100 and raising the high precision alignment arm.

[0182] To further mechanically stabilize the first ferrule 112 to thehead region 302 of the flexible printed circuit board 102, a dam 120 maybe formed on the flexible printed circuit board 102 and filled with thesecond adhesive 122. A software-controlled dam and dam fill dispensingmachine may be used to apply the dam 120 on the first surface 310 of thehead region 302 of the flexible printed circuit board 102.Alternatively, the dam and filling process may be done manually. The dam120 is formed on the first surface 310 of the head region 302 of theflexible printed circuit board 102 surrounding the first ferrule 112,driver or amplifier chip 108 and any other electrical components. Thedam 120 is composed of an adhesive .

[0183] Once the dam 120 is formed on the flexible printed circuit board102, the automated fluid dispensing machine may be used to fill the areawithin the dam 120 with the second adhesive 122, as shown in FIG. 3a.The second adhesive 122 may be cured by placing the flexible printedcircuit board 102 in an oven. After curing, the first ferrule 112becomes further mechanically stabilized to the first surface of the headregion 302 of the flexible printed circuit board 102.

[0184] F. Automating the Alignment Process

[0185] The entire process of precisely aligning and attaching the firstferrule 112 to the optoelectronic devices 106 and mechanicallystabilizing it to the flexible printed circuit board 102 may be donemanually. Alternatively, this process may be done automatically throughthe use of a computer generated system that functions in concert withthe above-described precision equipment. Accordingly, this process iscompatible with a mass-production manufacturing process that is the typeof technology that is necessary to lower the cost of anycommercially-available high-volume product.

[0186] G. Other Applications

[0187] Although an embodiment of the invention has been discussed interms of accurately aligning and attaching an array of optical fibers toan array of optoelectronic devices, the same methodology may be employedto accurately align and connect an array of optical fibers to a widevariety of devices or objects other than optoelectronic devices. This isbecause there is a trend to miniaturization in many fields of scienceand technology that require work pieces to be positioned to a fewmicrons and many times to sub-microns. Such fields include optics,microscopy, semiconductor technology, micro-machining, the life sciencesand others. Accordingly, an embodiment of the invention may be used, forexample, to accurately align and connect optical fibers to a microscopeslide so as to study fluorescence light emitted from a biological samplesuch as a gene or insect. The light may be collected by the opticalfibers and transmitted to a spectrometer for study. In another example,an embodiment of the invention may be used to accurately align andconnect an array of optical fibers to micro-electromechanical systems(“MEMS”). MEMS technology involves combining semiconductor andmicro-machining processes to produce tiny devices that are capable ofmotion on a microscopic scale on a silicon substrate. These systems mayutilize the technology contained in an embodiment of the invention toaccurately align and connect an array of optical fibers to the tinydevices in the micro-electromechanical system for a wide variety ofapplications. Consequently, an embodiment of the invention may be usedto couple an array of optical fibers to a wide variety of devices orobjects.

[0188] Finally, although an embodiment of the invention has beendiscussed in terms of passive alignment, an embodiment of the inventionallows for active alignment and attachment of the array of opticalfibers to an array of optoelectronic devices. As explained earlier, thisprocess involves manually manipulating and connecting the optical fibersto the optoelectronic devices.

[0189] While we have described our preferred embodiments of the presentinvention, it is understood that those skilled in the art, both now andin the future, may make various improvements and enhancements that fallwithin the scope of the claims that follow. These claims should beconstrued to maintain the proper protection for the invention firstdisclosed.

What is claimed:
 1. An apparatus comprising: a) a mounting structure; b)an array of optoelectronic devices adapted to the mounting structure,the optoelectronic devices having at least a first end; c) an array ofoptical elements, the array of optical elements having at least a firstend; d) the first end of the array of optical elements positionedrelative to the first end of the array of optoelectronic devices in sucha manner that one or more optical elements is optically aligned to oneor more optoelectronic devices; and e) a heat spreader positioned alongat least a portion of a surface of the mounting structure.
 2. Anapparatus as in claim 1, further comprising at least one opening in themounting structure, the opening functioning to provide thermal access tothe heat spreader.
 3. An apparatus as in claim 1, further comprising atleast one thermal via in the mounting structure, the thermal viafunctioning to transmit heat from the mounting structure to the heatspreader.
 4. An apparatus as in claim 1, further comprising at least oneheat pipe in the mounting structure, the heat pipe functioning totransmit heat from the mounting structure to the heat spreader.
 5. Anapparatus as in claim 1, wherein the heat spreader provides mechanicalrigidity or stiffness to the mounting structure.
 6. An apparatus as inclaim 1, wherein the array of optoelectronic devices comprises verticalcavity surface emitting lasers.
 7. An apparatus as in claim 6, whereinthe vertical cavity surface emitting lasers comprise oxide verticalcavity surface emitting lasers.
 8. An apparatus as in claim 1, whereinthe array of optoelectronic devices comprises photodetectors.
 9. Anapparatus as in claim 1, wherein the optical elements are opticalfibers.
 10. An apparatus as in claim 1, wherein the optical elements arelenses.
 11. An apparatus as in claim 1, wherein the array of opticalelements is a lenslet array.
 12. An apparatus as in claim 1, wherein theoptical elements are diffractive optical elements.
 13. An apparatus asin claim 1, wherein the optical elements are filters.
 14. An apparatusas in claim 1, wherein the optical elements are packaged in a ferrule.15. An apparatus as in claim 1, wherein the mounting structure is aflexible printed circuit board.
 16. An apparatus comprising: a) amounting structure; b) an array of optoelectronic devices adapted to themounting structure, the optoelectronic devices having at least a firstend; c) an array of optical elements, the array of optical elementshaving at least a first end; d) the first end of the array of opticalelements positioned relative to the first end of the array ofoptoelectronic devices in such a manner that one or more opticalelements is optically aligned to one or more optoelectronic devices; ande) an electrical plane positioned along at least a portion of a surfaceof the mounting structure.
 17. An apparatus as in claim 16, wherein theelectrical plane further comprises an electrical contact and groundplane.
 18. An apparatus as in claim 16, wherein the electrical planefunctions as an electrical contact path to at least one electrical oroptoelectronic component on the mounting structure.
 19. An apparatus asin claim 16, wherein the electrical plane functions to limitelectromagnetic interference to at least one electrical oroptoelectronic component on the mounting structure.
 20. An apparatus asin claim 16, wherein the electrical plane provides mechanical rigidityor stiffness to the mounting structure.
 21. An apparatus as in claim 16,wherein the array of optoelectronic devices comprises vertical cavitysurface emitting lasers.
 22. An apparatus as in claim 21, wherein thevertical cavity surface emitting lasers comprise oxide vertical cavitysurface emitting lasers.
 23. An apparatus as in claim 16, wherein thearray of optoelectronic devices comprises photodetectors.
 24. Anapparatus as in claim 16, wherein the optical elements are opticalfibers.
 25. An apparatus as in claim 16, wherein the optical elementsare lenses.
 26. An apparatus as in claim 16, wherein the array ofoptical elements is a lenslet array.
 27. An apparatus as in claim 16,wherein the optical elements are diffractive optical elements.
 28. Anapparatus as in claim 16, wherein the optical elements are filters. 29.An apparatus as in claim 16, wherein the optical elements are packagedin a ferrule.
 30. An apparatus as in claim 16, wherein the mountingstructure is a flexible printed circuit board.
 31. An apparatuscomprising: a) a mounting structure, b) an array of optoelectronicdevices adapted to the mounting structure, the optoelectronic deviceshaving at least a first end; c) an array of optical elements, the arrayof optical elements having at least a first end; d) the first end of thearray of optical elements positioned relative to the first end of thearray of optoelectronic devices in such a manner that one or moreoptical elements is optically aligned to one or more optoelectronicdevices; and e) a height adjuster positioned along at least a portion ofa surface of the mounting structure.
 32. An apparatus as in claim 31,wherein the height adjuster functions to change or control the height ofat least one optical, electrical or optoelectronic component on themounting structure.
 33. An apparatus as in claim 31, wherein the heightadjuster provides mechanical rigidity or stiffness to the mountingstructure.
 34. An apparatus as in claim 31, wherein the array ofoptoelectronic devices comprises vertical cavity surface emittinglasers.
 35. An apparatus as in claim 34, wherein the vertical cavitysurface emitting lasers comprise oxide vertical cavity surface emittinglasers.
 36. An apparatus as in claim 31, wherein the array ofoptoelectronic devices comprises photodetectors.
 37. An apparatus as inclaim 31, wherein the optical elements are optical fibers.
 38. Anapparatus as in claim 31, wherein the optical elements are lenses . 39.An apparatus as in claim 31, wherein the array of optical elements is alenslet array.
 40. An apparatus as in claim 31, wherein the opticalelements are diffractive optical elements.
 41. An apparatus as in claim31, wherein the optical elements are filters.
 42. An apparatus as inclaim 31, wherein the optical elements are packaged in a ferrule.
 43. Anapparatus as in claim 31, wherein the mounting structure is a flexibleprinted circuit board.
 44. An apparatus comprising: a) a mountingstructure; b) a heat spreader passing along a surface of a head regionof the mounting structure; c) a window in the head region of themounting structure, the window functioning to provide access to the heatspreader; d) an array of optoelectronic devices adapted to the heatspreader in such a manner that the array of optoelectronic devices isaccessible through the window in the mounting structure; e) an array ofoptical elements, the array of optical elements having at least a firstend; f) the first end of the array of optical elements positionedrelative to the first end of the array of optoelectronic devices in sucha manner that one or more optical elements is optically aligned to oneor more optoelectronic devices; and
 45. An apparatus as in claim 44,wherein the heat spreader provides mechanical rigidity or stiffness tothe mounting structure.
 46. An apparatus as in claim 44, wherein thearray of optoelectronic devices comprises vertical cavity surfaceemitting lasers.
 47. An apparatus as in claim 46, wherein the verticalcavity surface emitting lasers comprise oxide vertical cavity surfaceemitting lasers.
 48. An apparatus as in claim 44, wherein the array ofoptoelectronic devices comprises photodetectors.
 49. An apparatus as inclaim 44, wherein the optical elements are optical fibers.
 50. Anapparatus as in claim 44, wherein the optical elements are lenses . 51.An apparatus as in claim 44, wherein the array of optical elements is alenslet array.
 52. An apparatus as in claim 44, wherein the opticalelements are diffractive optical elements.
 53. An apparatus as in claim44, wherein the optical elements are filters.
 54. An apparatus as inclaim 44, wherein the optical elements are packaged in a ferrule.
 55. Anapparatus as in claim 44, wherein the mounting structure is a flexibleprinted circuit board.
 56. An apparatus comprising: a) a mountingstructure; b) a height adjuster passing along a surface of a head regionof the mounting structure; c) a window in the head region of themounting surface, the window functioning to provide access to the heightadjuster; d) an array of optoelectronic devices adapted to the heightadjuster in such a manner that the array of optoelectronic devices isaccessible through the window in the mounting structure; e) an array ofoptical elements, the array of optical elements having at least a firstend; and f) the first end of the array of optical elements positionedrelative to the first end of the array of optoelectronic devices in sucha manner that one or more optical elements is optically aligned to oneor more optoelectronic devices.
 57. An apparatus as in claim 56, whereinthe height adjuster provides mechanical rigidity or stiffness to themounting structure.
 58. An apparatus as in claim 56, wherein the arrayof optoelectronic devices comprises vertical cavity surface emittinglasers.
 59. An apparatus as in claim 58, wherein the vertical cavitysurface emitting lasers comprise oxide vertical cavity surface emittinglasers.
 60. An apparatus as in claim 56, wherein the array ofoptoelectronic devices comprises photodetectors.
 61. An apparatus as inclaim 56, wherein the optical elements are optical fibers.
 62. Anapparatus as in claim 56, wherein the optical elements are lenses. 63.An apparatus as in claim 56, wherein the array of optical elements is alenslet array.
 64. An apparatus as in claim 56, wherein the opticalelements are diffractive optical elements.
 65. An apparatus as in claim56, wherein the optical elements are filters.
 66. An apparatus as inclaim 56, wherein the optical elements are packaged in a ferrule.
 67. Anapparatus as in claim 56, wherein the mounting structure is a flexibleprinted circuit board.
 68. An apparatus comprising: a) a mountingstructure; b) an electrical plane passing along a surface of a headregion of the mounting structure; c) a window in the head region of themounting structure, the window functioning to provide access to theelectrical plane; d) an array of optoelectronic devices adapted to theelectrical plane in such a manner that the array of optoelectronicdevices is accessible through the window in the mounting structure; e)an array of optical elements, the array of optical elements having atleast a first end; and f) the first end of the array of optical elementspositioned relative to the first end of the array of optoelectronicdevices in such a manner that one or more optical elements is opticallyaligned to one or more optoelectronic devices.
 69. An apparatus as inclaim 68, wherein the electrical plane further comprises an electricalcontact and ground plane.
 70. An apparatus as in claim 68, wherein theelectrical plane functions as an electrical contact path to at least oneelectrical or optoelectronic component on the mounting structure.
 71. Anapparatus as in claim 68, wherein the electrical plane functions tolimit electromagnetic interference to at least one electrical oroptoelectronic component on the mounting structure.
 72. An apparatus asin claim 68, wherein the electrical plane provides mechanical rigidityor stiffness to the mounting structure.
 73. An apparatus as in claim 68,wherein the array of optoelectronic devices comprises vertical cavitysurface emitting lasers.
 74. An apparatus as in claim 73, wherein thevertical cavity surface emitting lasers comprise oxide vertical cavitysurface emitting lasers.
 75. An apparatus as in claim 68, wherein thearray of optoelectronic devices comprises photodetectors.
 76. Anapparatus as in claim 68, wherein the optical elements are opticalfibers.
 77. An apparatus as in claim 68, wherein the optical elementsare lenses.
 78. An apparatus as in claim 68, wherein the array ofoptical elements is a lenslet array.
 79. An apparatus as in claim 68,wherein the optical elements are diffractive optical elements.
 80. Anapparatus as in claim 68, wherein the optical elements are filters. 81.An apparatus as in claim 68, wherein the optical elements are packagedin a ferrule.
 82. An apparatus as in claim 68, wherein the mountingstructure is a flexible printed circuit board.